Nuveen California Select Tax-Free Income Portfolio is a closed-ended investment company. The Fund seeks to provide current income and stable dividends, exempt from regular federal and designated state income taxes, where applicable, consistent with the preservation of capital by investing primarily in a portfolio of municipal obligations. The Fund invests in municipal securities that are exempt from federal and California state income taxes. The Fund invests at least 80% of its managed assets in securities rated, at the time of investment, investment grade (Baa/BBB or better by S&P, Moody's, or Fitch). The fund may invest in inverse floating rate municipal securities, also known as tender option bonds. Nuveen Fund Advisors, LLC, formerly known as Nuveen Fund Advisors, Inc, is the Fund's Adviser.